This disclosure relates to a gas turbine engine airfoil. More particularly, the disclosure relates to a cooling configuration in an airfoil.
Gas turbine engines typically include a compressor section, a combustor section and a turbine section. During operation, air is pressurized in the compressor section and is mixed with fuel and burned in the combustor section to generate hot combustion gases. The hot combustion gases are communicated through the turbine section, which extracts energy from the hot combustion gases to power the compressor section and other gas turbine engine loads.
Both the compressor and turbine sections may include alternating series of rotating blades and stationary vanes that extend into the core flow path of the gas turbine engine. For example, in the turbine section, turbine blades rotate and extract energy from the hot combustion gases that are communicated along the core flow path of the gas turbine engine. The turbine vanes, which generally do not rotate, guide the airflow and prepare it for the next set of blades.
Many blades and vanes, blade outer air seals, turbine platforms, and other components include internal cooling passages having a tortuous flow path including turns that provide a serpentine shape, which create undesired pressure losses. Some of the cooling passages may include portions having turbulence promoters that enhance the cooling effects of the cooling flow through the cooling passage.
Gas turbine engines frequently utilize turbine inlet temperatures well beyond the incipient melting point of the component constituent materials due to the push for higher operating efficiencies. To slow or prevent the destruction of hardware, dedicated cooling air is withdrawn from the compressor and used to cool both static and rotating components in the gas path that are at risk of succumbing to damage or failure at elevated temperatures.
When the cooling air is reintroduced into the turbine, significant cycle penalties occur, particularly in the low pressure turbine. Therefore, it is attractive to utilize the extracted cooling air as efficiently as possible to cool turbine components. Both static and rotating components rely on this cooling air. This cooling air has a significantly lower temperature than the walls of the component, which allows for heat to be removed convectively from the walls into the air. A variety of internal features are used to improve the convective heat transfer coefficient as the cooling air flows through the component including, but not limited to: pedestals, impingement ribs, and trip strips. These features, by themselves, are frequently inadequate means of cooling the component, and rely on cooling holes and slots to release the cooling air into the gas path, creating a film to protect the component against the high temperatures of the gas path at the cost of lowered efficiency.
One cooling configuration for efficient use of channel flow heat transfer is a serpentine cooling passage, typically with three or more radial passes through an airfoil creating a circuit. The downside to traditional serpentines is that for blades with larger section widths, a larger-scaled channel size does not carry the same cooling mass flow efficiency as narrower channels.